The present invention relates to machines for packaging objects, such as cookies and particularly to apparatus for controlling the speed of operation of such machines. When controlling the speed of a packaging machine, care must be taken that the objects to be packaged, which are generally furnished by a source which is subject to fluctuations in its output rate, are fed into the machine in such a way that they are positively gripped by the machine and subsequently packaged. For this purpose it is necessary for the objects to accumulate to some extent on the input path to the machine so that they will be available at its entrance in immediate succession, i.e. in uninterrupted sequence.
The objects being packaged may be, for example, delicate cookies and in order to prevent the development of unduly high pressures which could damage such objects, the number of objects which can accumulate should be limited. In order to accomplish this, the speed of the packaging machine must be adapted to the output of the source.
The source may also not be providing any objects, i.e. have no output at all, as may occur, for example, at the end of a production shift or as a result of a malfunction. In this case, the packaging machine must be stopped and restarted after production resumes or after elimination of the malfunction.
The speed of the packaging machine is often adapted manually in a very simple manner by observing the length of the accumulation on the input path and if it is more or less than a given length, the speed of the packaging machine is increased or decreased by means of a manual control.
To avoid the labor expenses which such regulation requires, an apparatus has been developed to control the speed of a packaging machine with the aid of sensors which are disposed along the input paths for the machine for the purpose of determining whether or not an uninterrupted series of objects to be packaged is present at certain points along this path. The rate of rotation of the motor driving the machine is then controlled in steps in dependence on the sensor signals so that over the operating range of the machine all objects introduced to it at a fluctuating feeding speed are permitted to accumulate to a certain extent in front of the machine and are then packaged by the machine at a rate, and with a rhythm, determined by its speed.
This known control apparatus has the drawbacks that it is rather complicated and nevertheless provides insufficiently rapid adaptation of the machine speed to changes in the rate of delivery of objects. Three sensors are required and the speed is adjusted only to two limit values, i.e. to an upper limit value when the length of accumulation has reached a given maximum, and to a lower limit value when it has reached a given minimum. This results in considerable undesirable fluctuations in the accumulation pressure.